Electronic devices such as smart phones, tablets, desktop computers, laptop computers, televisions, and other electronics contain a significant amount of valuable metals. End-of-life electronic devices (also referred to as electronic waste, or so-called “e-waste”) contain metals including base metals (e.g., zinc, tin, lead, nickel, and copper) and precious metals (e.g., silver, gold, palladium) in electronic circuitry of such devices. For example, electronic devices may include circuitry connected by copper traces, nickel leads and terminals, nickel plating on conductive traces, solder (which may include tin, silver, copper, and combinations thereof) used to form electrical connections between conductive components, surface contacts coated with gold, and capacitors including silver and palladium. The electronic devices also include rare earth magnets formed from rare earth elements (e.g., neodymium, yttrium, samarium, etc.) within circuitry, speakers, displays, storage devices (e.g., hard disk drives), vibrating components of telephones, and other electronic components of the device.
Currently, the metals contained in electronic waste are not sufficiently recovered prior to disposing the electronic waste. In some instances, the electronic waste is landfilled or combusted (e.g., incinerated) without recovering a significant portion of the metals therein. Landfilling the electronic waste has the potential to contaminate soil and underground water. The combustion process may release toxic compounds (e.g., lead) into the atmosphere.
Methods of recycling the metals in the electronic waste have been proposed. Such methods include leaching the electronic waste with a strong acid which includes dissolving a majority, if not all, of the metals in the electronic waste in a single leaching solution (leachate). However, it is difficult to recover substantially pure metals of each of the metals dissolved in the leachate. In addition, the leaching process produces hydroxide ions that increase a pH of the leachate and consume a significant amount of the acid therein. To compensate for the increase in pH, additional fresh acid is added to the leachate, undesirably consuming a significant amount of the acid.
Accordingly, there is a continuing need for methods of recovering substantially pure metals from electronic waste without consuming large amounts of acid while recovering substantially pure elemental metals.